Various image pickup modules, each of which includes a solid-state image pickup device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) etc., have been developed. Specific examples of the image pickup modules include compact digital cameras and compact digital camcorders etc. In particular, image pickup modules for use in portable terminals (personal digital assistant and mobile phones etc.), which have come into widespread use in recent years, are required to produce high-resolution images and to be small in size and low in height.
A technique of reducing the size and height of an image pickup lens for use in an image pickup module, which is for reducing the size and height of the image pickup module, is attracting attention. Patent Literatures 1 to 3 disclose specific examples of such a technique.
Patent Literature 1 discloses an image pickup lens constituted by a lens system including an aperture diaphragm, a first lens, and a second lens arranged in this order from an object side. The first lens is a meniscus lens (i) whose surface facing toward the object has a convex shape and (ii) which has positive refractive power. The second lens has two concave surfaces. Each of the first and second lenses has at least one aspheric surface. In addition, the image pickup lens satisfies the following conditions:0.6<f1/f<1.0  (A)1.8<(n1−1)f/r1<2.5  (B)
where f is the focal length of the lens system (image pickup lens), f1 is the focal length of the first lens, n1 is the refractive index of the first lens, and r1 is the curvature radius of an object side surface of the first lens.
Patent Literature 2 discloses an image pickup lens constituted by an aperture diaphragm, a first lens, and a second lens arranged in this order from an object side to an image surface side. The first lens is a meniscus-shaped lens (i) whose convex surface faces toward the object and (ii) which has positive refractive power. The second lens has (a) two concave surfaces and (b) negative refractive power. The image pickup lens satisfies the following conditions (C) through (F):0.8<ν1/ν2<1.2  (C)50<ν1  (D)1.9<d1/d2<2.8  (E)−2.5<f2/f1<1.5  (F)
where
ν1 is the Abbe number of the first lens,
ν2 is the Abbe number of the second lens,
d1 is the thickness of the first lens at its center,
d2 is a distance from the image side surface of the first lens image surface to the object side surface of the second lens,
f1 is the focal length of the first lens, and
f2 is the focal length of the second lens.
Patent Literature 3 discloses an image pickup lens constituted by an aperture diaphragm, a first lens, and a second lens arranged in this order from an object side to an image surface side. The first lens is a meniscus-shaped lens (i) whose convex surface faces toward the object and (ii) which has positive refractive power. The second lens has (a) two concave surfaces and (b) negative refractive power. The image pickup lens satisfies the following conditions (G) and (H):−2.5<f2/f1<−0.8  (G)0.8<ν1<ν2<1.2  (H)
where
f1 is the focal length of the first lens,
f2 is the focal length of the second lens,
ν1 is the Abbe number of the first lens, and
ν2 is the Abbe number of the second lens.